Bonding is an important process in the fabrication of many industrial, electronic, biological and optical devices. Typically bonding is accompanied by pressure together with heat, electrical field or both heat and field. A plurality of layers to be bonded are stacked in a loose assembly and pressed together. They are then subjected to heat and/or an electric field under pressure. The heat and/or field may effectuate the formation of chemical bonds as in ionic bonding.
The usual method of pressing the layers together is to stack the layers in an assembly and dispose the assembly on respective rigid plates of a mechanical press. This technique, however, has serious limitations in bonding layers of large area or imperfect planarity. Even high precision mechanical presses present tolerance problems over large areas. Presses move on guide shafts through apertures, and the spacings between the shafts and their respective apertures permit undesirable relative translational and rotational shifts between the assembly and the plates. Thus mechanical presses present serious alignment problems in high precision bonding. Moreover, despite the most careful construction, the layers to be bonded are not perfectly planar. When assemblies of these layers are disposed on the rigid plates of a press, the deviations from planarity over large areas can result in variations in the bonding pressure and spacing. Accordingly, it is desirable to provide a method of bonding which avoids the limitations of mechanical presses.